陕西关中农田土壤中塑料碎片和微塑料残留及其累积特征研究

Residues and accumulation characteristics of plastic fragments and microplastics in farmland soil of Guanzhong Plain, Shaanxi

  • 摘要: 农膜覆盖技术的应用及推广促进了干旱半干旱地区农业的发展, 然而农膜残留及其碎片造成的土壤污染问题, 已成为绿色农业发展及生态安全面临的重要挑战。本研究以陕西关中平原为研究区域, 通过野外调研采集不同作物种植农田耕层土壤(0~30 cm), 利用检视法、密度分离法及显微镜扫描鉴定等技术, 研究长期农膜覆盖蔬菜地(蔡家坡, 以下简称蔬菜地)与大棚(苗圃)种植区(杨凌, 以下简称大棚区)土壤中塑料残片和微塑料残留及累积丰度特征。结果表明: 研究区域土壤中均检出塑料残片, 塑料残片颜色主要有红色、黑色、白色、蓝色等, 其中蔬菜地以白色农膜残片为主, 而大棚区主要以黑色培养钵碎片为主; 不同土层中, 塑料残片随着土层深度的增加而显著减少(P<0.05), 且残片个数随着残片面积的增大而减小, 其中蔬菜地37.8%为0.25~2 cm2的小残片, 其次为2~10 cm2、10~25 cm2的残片, 最低为>25 cm2的大残片; 大棚区67.5%为0.25~2 cm2的残片, 其次为2~10 cm2、10~25 cm2的残片, 几乎未检测到>25 cm2的大残片塑料。同时, 残片含量随土层深度增加而显著减小(P<0.05), 0~10 cm土壤中蔬菜地残片含量平均为26.2 μg∙g−1, 大棚区平均为34.9 μg∙g−1; 而20~30 cm土层中残片含量最低, 蔬菜地仅为2.48 μg∙g−1, 大棚区平均为4.79 μg∙g−1。然而, 蔬菜地微塑料检出率较低, 为23.9%, 且最大检测量为表层0~10 cm, 为1.8×103个∙kg−1; 而在大棚区微塑料检出率为39.5%, 最大检测量为表层0~10 cm, 为500个∙kg−1。由此看出, 长期施用农膜及塑料大棚导致土壤中塑料残留量显著增大, 且不同土层中塑料残片及微塑料累积量变化差异较大, 可能对土壤性质及作物生长造成危害, 导致土壤肥力和作物产量下降等不良后果。后续应进一步对塑料残留碎片化过程及微塑料在土体内迁移和累积风险进行研究, 以期为全面评估该区域农田土壤塑料污染提供依据。

     

    Abstract: The application and extension of agricultural film-mulching technology has greatly promoted the development of agriculture in arid and semi-arid areas. However, soil pollution caused by agricultural film residues and their fragmentation have become a great challenge to the development of green agriculture and sustenance of ecological security. In this study, the topsoil (0−30 cm) of farmland from the Guanzhong Plain in Shaanxi Province planted with different crops was taken through field investigation, and samples were analyzed using advanced plastic fragments and microplastic extraction and microscopic scanning identification method to study the characteristics of plastic fragments and microplastics and accumulation in two case study areas: vegetable cultivation area in Caijiapo (S1) and greenhouse planting area in Yangling (S2). The results showed that plastic fragments were detected in all the soil samples, and the residue color was red, black, white, and blue in the vegetable planting area. In the greenhouse planting area, the residues from the culture cups were mainly black. The number of plastic fragments decreased significantly with increasing soil depth (P<0.05) and increasing area. Specifically, in the vegetable planting area, 37.8% of the fragments were in the 0.25−2 cm2 group, followed by those in the 2−10 cm2 and 10−25 cm2 groups, and the lowest fragment group was >25 cm2. In the greenhouse planting area, 67.5% of the debris was in the 0.25−2 cm2 group, followed by that in the 2–10 cm2 and 10–25 cm2 groups, and large plastic residue (>25 cm2) was almost not detected. In the different soil layers, the content of plastic residues decreased significantly with increasing soil depth (P<0.05). Specifically, the content of residues in the 0−10 cm soil of S1 and S2 was 26.2 μg·g−1 and 34.9 μg·g−1, respectively, and the residual content in 20−30 cm soil layer was the lowest; it was 2.48 μg∙g−1 in vegetable plot and 4.79 μg∙g−1 in greenhouse nursery. However, the detection rate of microplastics in the vegetable growing area was 23.9%, with a maximum of 1.8×103 particles·kg−1 in the 0–10 cm soil layer of S1-2. In the greenhouse planting area, the detection rate of microplastics was 39.5%, with a maximum of 500 particles·kg−1 in the 0–10 cm soil layer of S2-2. In conclusion, the long-term application of agricultural plastic film and plastic products in agriculture leads to an increase in plastic residues in farmland soil. Significant differences in plastic residue and microplastic accumulation were found in different soil layers, and they may be harmful to soil properties and crop growth, reducing soil fertility, declining crop yield, and causing other adverse consequences. Therefore, further studies are needed to understand the fragmentation process of plastic residues and the cumulative and migration risk of microplastics in soil to provide a survey-based dataset for comprehensive assessment of plastic pollution in the Guanzhong Plain.

     

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